Investigating the effect of aging on transpassive behavior of Ni-based alloys in sulfuric acid with shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS)

The effect of high temperature aging on the electrochemical behavior of Ni superalloys has implications for their use in Generation IV nuclear reactors. Linear sweep voltammetry, shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS), and X-ray photoelectron spectroscopy (XPS) were used to interrogate the passivation layer formed on heat-treated and as-received samples of Inconel 617 and Haynes 230. Results demonstrate that heat treatment improves electrochemical corrosion resistance for both alloys. The improved electrochemical behavior is associated with differences in the spectra; specifically, the appearance of a mixed Cr(III/VI) oxide.

► Correlation between transpassive current density and observation of surface Cr species in the Raman spectra.
► In both alloys 617 and 230, heat treatment resulted in delayed onset of the transpassive region.
► Spectroscopy shows heat treatment makes more Cr available to the surface.